SEA-WORMS. Ill 



colour as the light is variously reflected from the finely-toothed 

 threads. 



We must use the lens if we are to get an idea of the struc- 

 ture of this beautiful crown. By its aid we find there are a 

 great number of filaments, each one fringed with finer pro- 

 cesses on each side. Fine as these are, they are all hollow, 

 and through them the blood constantly flows, to be brought in 

 contact with, and to absorb the oxygen of the sea-water, which 

 can pass through the microscopic meshes of their walls through 

 which, however, the free cells of the blood cannot pass. In 

 some species these gills are arranged not in circular form but 

 spirally round a central shaft. 



Among the numerous species of Sabella to be found on our 

 shores, there is one that is not inaptly termed the Silkworm 

 Sabella (S. bombyx], and indeed, being a real worm it has 

 more claim to the title than has the caterpillar that is called 

 the Silkworm. This silk-producing Sabella, however, could 

 scarcely be pressed into the service of man, though one could 

 fancy an imaginative writer employing this spinner to make 

 gossamer vestments for sea-fairies, for the material produced 

 is of just the texture a fairy would desire. Not long ago, I 

 introduced to one of my aquarium vases a flat stone that 

 supported a sea-anemone, which I was loth to disturb, and 

 would rather he moved off on his own account. In doing this, 

 one never knows what one may be introducing in addition to 

 the specimen desired, unless one takes the precaution of 

 scraping or scrubbing the stone. A. week or two later, I was 

 surprised one morning to find several threads so clear as to 

 be scarcely visible running up from this stone at the bottom 

 to a point about four inches up the glass. Next day there was 

 more of it, and so on from day to day the quantity increased, 

 and the older portion became more visible than before, for its 

 extreme transparency passed away, and it became dusty-look- 

 ing in fact, cobwebby. By this time it was clear that what 

 had at first looked like purposeless threads and filaments were 

 really part of a quite voluminous tube. 



